This was probably my biggest epiphany when I started studying biochemistry. Later on, and in my current bubble of natural scientists it is fairly obvious to everyone, but back then it was a huge thing for me. The fact, that life as we know it only exists in water. If you’re not already bored or you’re thinking “I’m no frickin fish dude, I am living on land you d*** f***”, then stick with me and I will guide through what exactly I mean with this (and also: rude?!?)
Life, from a formal point of view, is not the emergence of many-legged species that contemplate about the meaning of life or play candy crush (is that still a thing?), but it is about …
Pause here for a second and think about how you would define life …
… Okay done? Keep going
There are several definitions about life out there, but in general, we can all agree that any living system must have some necessary features like reproduction, metabolism, compartmentalisation, adaptation and maybe some more. Viruses for example don’t have their own metabolism, so some definitions exclude them from the realm of the living. Does that make them undead?
All these features are basically phenomena driven by complex chemical reactions that happen inside the cells of that living organism. And here comes my point. All these biochemical reactions happen in water. So when I say life exists only in water, I am not speaking about where the organisms live. They occur obviously both surrounded by air (on land) and in water. I am speaking about where the biochemistry occurs that is the basis for all life. And the solvent for that (as the chemists say), is exclusively water.
We are 60% water. It acts (mainly) as the solvent that our biochemical reactions happen in. Our cells can not be in contact with air, because drying out means that the chemistry doesn’t work anymore. Also, oxygen is actually really toxic to us (but that is maybe a topic for a separate post). All our cells in contact with air are either dead (our skin cells) or they are kept moisturised, like our eyes and mucosa in other bodily openings (sounds pretty gross). Hair isn’t made of cells, in case you were wondering. They are just long chains of pretty tough protein.
So in a way, we’re water-based organisms that walk around in a space suit of dead cells. Somehow, we became dependent on that oxygen around us, so going back to water isn’t really an option anymore. Long term at least. I hope everyone takes a bath here and there.
Musical inspiration: Linkin Park – War. You can say what you want about post-Meteora Linkin Park, but the band surely evolved a lot and this album definitely marks a peak for me. I wish I had a bathtub right now 🙁
Some random thoughts on extraterrestrial life and water:
The strong dependence of life on water raises several questions. Why water? And: only water? You can imagine, I can’t really give you a plain answer on these questions. However, water is a very special substance and we know a lot about it. In general, people assume water is crucial for the formation of life, because of its unique features (keyword for the curious: anomaly of water). For example, it freezes from the top down because of the low density of ice. Also, it’s really reactive and actively participates in a lot of reactions, unlike many other solvents in chemistry. The second question depends a bit on our definition of life. If we’re talking about carbon-based life (same question here: why carbon? But answering that is a bit more technical), water is assumed to be crucial. It’s also the only liquid on Earth, if you think about it. But on other planets, we find other liquids, like methane on Titan. However, they’re all lacking the great features of water, so we generally assume it’s not as straight forward. However, none of the defining properties if life must inevitably lead to what you find on Earth. It could be much slower, much bigger or otherwise different in many ways but still satisfy all those criteria.
I’m no expert in this field, I just had some random thoughts on the matter. If you think you know more or disagree with me, shoot me a message and tell me your thoughts on the matter.